Reference Values for Macronutrients in Human Milk: the Mothers, Infants and Lactation Quality (MILQ) Study

This second article in the series establishing reference values (RVs) for nutrients in human milk describes RVs for protein, carbohydrate, fat, and energy. To establish RVs, the mothers, infants, and lactation quality (MILQ) and early-MILQ studies collected human milk samples throughout the first 8.5 mo of lactation in 1242 well-nourished women in Bangladesh, Brazil, Denmark, and The Gambia. Macronutrients were measured by near-infrared spectroscopy. Protein concentrations decreased from 12.4 g/L at 4–17 d to a 7.7–7.9 g/L plateau by 4–5 mo. Carbohydrate concentrations were stable throughout lactation, ranging from 68.2 to 70.1 g/L. Fat concentrations decreased from 37.0 g/L at 4–17 d to 31.2–32.8 g/L after 2–3 mo. Energy density mirrored fat trends, decreasing from 665 kcal/L at 4–17 d to 597–602 kcal/L by 3–4 mo. Compared with estimates used by the Institute of Medicine (IOM)--renamed the National Academy of Medicine (NAM) in 2015--to set nutrient intake recommendations for infants, MILQ values were ∼90% of concentrations used for carbohydrate and energy, and 70%–80% for protein and fat. Total daily median intakes (concentrations × milk volumes) from 1 to 6 mo were on par with IOM adequate intakes (AIs) for carbohydrate and energy, 65% of the AI for protein, and 84% of the AI for fat. These RVs offer a critical resource for understanding the nutritional contributions of human milk and informing public health practices to support infant growth and development.